Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$9.70	13.693%	$11.0282	$11.03	$11.05	$11.00
Purchase #2	$206.82	12.715%	$233.1172	$233.12	$233.10	$233.10
Purchase #3	$179.99	9.309%	$196.7453	$196.75	$196.75	$196.70
Purchase #4	$37.93	6.576%	$40.4243	$40.42	$40.40	$40.40
Purchase #5	$155.97	8.234%	$168.8126	$168.81	$168.80	$168.80
Purchase #6	$186.64	13.774%	$212.3478	$212.35	$212.35	$212.30
Purchase #7	$183.77	8.328%	$199.0744	$199.07	$199.05	$199.10
7 purchase totals =	$960.82		$1,061.5498	$1,061.55	$1,061.50	$1,061.40